1. Field of the Invention
The invention relates generally to pipe connections, and more particularly to systems and methods for hydraulically actuating a pair of pipe flanges to cause them to be sealingly engaged.
2. Related Art
The use of pipelines for handling large volumes of fluids is widely known. High-volume pipelines are commonly used for fluid hydrocarbons such as oil or natural gas. The pipelines used in these applications typically consist of a number of pipe sections which are connected end-to-end to form a single conduit.
In many instances, these pipelines carry fluids that may be toxic, volatile, corrosive or otherwise dangerous. Often, it is necessary to pressurize the fluids that are carried by the pipelines. Because it may be potentially dangerous for fluids to escape from the pipelines, it is very important to ensure that the connections between pipe sections in the pipelines do not leak.
The integrity of the seal between two pipe sections in a pipeline depends on a number of factors, including the type of connection between the pipe sections, the type of gaskets or seals used in the connection, and even the manner in which the connection is assembled. The manner in which the connection is assembled is also an important factor in the reliability of the connection. Improper assembly of a connection may cause the connection to leak or to fail entirely.
Most conventional connections between pipe sections utilize flanges at the ends of the pipe sections that are bolted together with a seal ring or gasket between them. It is important in the assembly of these connections to ensure that the flanges are evenly tightened so that the load (the force holding the flanges together) is evenly distributed across the sealing faces of the flanges. If the distribution is uneven, less pressure may be applied on one side of the flanges, causing the connection to leak. Uneven distribution of force in a connection that uses bolts to hold the flanges together may also cause more heavily loaded bolts to fail, which may then lead to leaks or failure of additional bolts and/or the connection itself.
Because of the importance of evenly distributing the load across the sealing surfaces in the connection, it is typical in assembling conventional bolted-flange connections to check the torque on each of the bolts when the connection is assembled to ensure that each of the bolts carries nominally the same load. Changing conditions, however, may affect the loading on individual bolts so that, even if the bolts originally carried the same load, the individual loading of the bolts may change, causing uneven distribution of the force applied by the bolts around the connection.
Bolt tensioners provide an alternative mechanism for ensuring that force is evenly applied around the circumference of the flanges. A bolt tensioner is a hydraulically expandable device that is placed around an individual bolt, between the flange and a nut that is threaded onto the bolt. Hydraulic pressure is used to expand the tensioner until a known amount of force is applied by the tensioner between the nut and the flange. Typically, when bolt tensioners are used, an individual bolt tensioner is placed on each bolt, and the same hydraulic pressure is applied to each of the bolt tensioners in order to apply the same amount of force around the circumference of the flanges.
While this mechanism is helpful in ensuring that force is evenly distributed across the sealing faces of the connection without having to individually check the torque of each nut as it is tightened on to the corresponding bolt, it has its own drawbacks. For example, because it is necessary to install a tensioner on each of the bolts of the connection, the system of tensioners itself becomes a rather complicated hydraulic system. Because the bolt tensioning system may be very complex, it may be very expensive. Moreover, the complexity of the system carries with it an increased risk that it, too, may fail.
It would therefore be desirable to provide systems and methods for ensuring that force is evenly applied around the sealing faces of a connection which do not suffer from the drawbacks of the prior art.